Using our various diabetic, prediabetic, and aobese stocks of inbred mice, our objective is to study the interplay of genetic and environmental factors that modulate the entry of pancreatic beta cells into an atrophic, hyperplastic, or neoplastic state. We shall continue our studies of the biochemical expression in vitro of the genes diabetes (db) and obese (ob), studying cultured pancreatic endocrine cells from postnatal pancreas to determine whether glucagon hypersecretion of diabetic alpha 2 cells in vitro represents a primary genetic defect, or reflects prior stimulation in vivo by the hypothalamus-pituitary-adrenal endocrine axis. We shall also screen for the primary expression of the db and ob genes in cultured hepatocytes and adipocytes. We shall attempt to define the specific metabolic requirements for growth and division of normal and mutant pancreatic epithelial cells, and to produce cell lines of functional pancreatic endocrine cells for use in cell-replacement therapy studies in mice. By subjecting cultured pancreatic cells of both normal and mutant genotypes to simulated diabetogenic environments, as well as by exposing these cultures to certain murine viruses, we plan to study the role of environmental modulation of mutant gene expression as a function of genetic background. Finally, we shall conduct a thorough ultrastructural and biochemical analysis in vivo to characterize the cellular basis for pancreatic beta cell atrophy versus hyperplasia as a function of mutant gene expression on different genetic backgrounds.